Method for assembling a tiled, flat-panel microdisplay array

• US 6,476,886 B2
• Filed: 02/15/1999
• Issued: 11/05/2002
• Est. Priority Date: 02/15/1999
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Rainbow Displays, Inc.
• Inventors: Seraphim, Donald P., Krusius, J. Peter
• Primary Examiner(s): Parker, Kenneth
• Assistant Examiner(s): QI, ZHI QIANG
• Application Number:
  US09/250,486
• Publication Number:
  US 20020001051A1
• Time in Patent Office: 1,359 Days
• Field of Search: 349/73, 349/74, 349/122, 349/20, 349/21, 349/158, 349/153, 349/155, 349/190, 349/45, 349/103
• US Class Current: 349/73
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon

Abstract

This invention describes fabrication techniques for producing microdisplays suitable for combining into tiled, flat-panel displays having visually imperceptible seams. Assembly techniques to overcome flatness requirements imposed by tiled, flat-panel display assemblies are also described. Edge treatment techniques for individual microdisplays while still part of the silicon die or wafer are also described. The use of these inventive techniques allows the assembly microdisplays into tiled, flat-panel that are appear visually seamless and optically uniform.

Claims

1. A method for assembling a plurality of reflective microdisplay tiles into a tiled, flat-panel display, the projected image of which display having visually imperceptible seams in reflection, the steps comprising:

a) providing a plurality of reflective monolithic microdisplay tiles, each tile having a front, active face, a rear, mounting face, at least one inner, precision finished edge, each of said microdisplay tiles comprising an array of pixels having a predetermined pixel pitch and having a semiconductor integrated circuit backplane embedded therein;

b) laterally arranging said plurality of microdisplay tiles adjacent one another with said at least one inner, precision finished edge of a first one of said plurality of microdisplay tiles adjacent said at least one precision finished edge of a second one of said plurality of microdisplay tiles;

c) releasably attaching said front, active faces of said plurality of microdisplay tiles to an optically flat carrier;

d) after said laterally arranging step (b) and said releasably attaching step (c), applying a filling material to said rear faces of said plurality of tiles, if required, to fill any gaps between said inner, precision finished edges of said microdisplay tiles;

e) after completing said releasably attaching step (c), polishing said rear, mounting face of each of said plurality of microdisplay tiles, if required;

f) after completing said polishing step (e), attaching a common substrate to said rear, mounting faces of said plurality of microdisplay tiles; and

g) after said attaching step (f), removing said plurality of microdisplay tiles from said optically flat carrier and polishing said front active faces of each of said plurality of microdisplay tiles to a precision of less than approximately 100 nM.

2. The method for assembling a plurality of microdisplay tiles as recited in claim 1, wherein said optically flat carrier is a temporary substrate.

3. The method for assembling a plurality of microdisplay tiles as recited in claim 2, wherein said common substrate is a permanent substrate.

4. The method for assembling a plurality of microdisplay tiles as recited in claim 3, wherein said arranging step (b) comprises aligning said plurality of microdisplay tiles relative to at least one alignment mark.

5. The method of assembling a plurality of microdisplay tiles as recited in claim 4, wherein at least one of said plurality of tiles comprises a tile alignment mark, said tile alignment mark being compatible with said at least one alignment mark on said optically flat carrier.

6. The method for assembling a plurality of microdisplay tiles as recited in claim 4, the steps further comprising:

polishing a front face of said tiles and said filling material to a predetermined degree of flatness.

7. The method for assembling a plurality of microdisplay tiles as recited in claim 6, wherein said polishing step comprises chemical/mechanical polishing (CMP).

8. The method for assembling a plurality of microdisplay tiles as recited in claim 7, wherein said predetermined degree of flatness of said front face is within a dimension less than the wavelength of visible light.

9. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 8, wherein arranging said plurality of microdisplay tiles with respect to a direction perpendicular to said faces results in tile-to-tile differences in said perpendicular direction of said tiles smaller than the distance between said faces thereof.

10. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 9, wherein tile-to-tile differences in said perpendicular direction of said tiles in said arrangement is less than one half the distance between said faces thereof.

11. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 9, wherein tile-to-tile differences in said perpendicular direction of said tiles in said arrangement is less than one quarter the distance between said faces thereof.

12. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 9, wherein tile-to-tile differences in said perpendicular direction of said tiles in said arrangement is less than one tenth the distance between said faces thereof.

13. The method for assembling a plurality of microdisplay tiles as recited in claim 4, wherein said releasably attaching step (c) comprises using a vacuum technology.

14. The method for assembling a plurality of microdisplay tiles as recited in claim 4, wherein said releasably attaching step (c) comprises using an adhesive technology.

15. The method for assembling a plurality of microdisplay tiles as recited in claim 14, wherein said releasably attaching step (c) comprises curing media with one or more of the set of heat, infrared energy, ultraviolet light, pressure, chemical reaction and time.

16. The method for assembling a plurality of microdisplay tiles as recited in claim 3, wherein said laterally arranging step (b) comprises registering said plurality of microdisplay tiles relative to at least one mechanical stop.

17. The method for assembling a plurality of microdisplay tiles as recited in claim 16, wherein said mechanical stop is constructed from one from the group of polymers, ceramics, glass and metals.

18. The method for assembling a plurality of microdisplay tiles as recited in claim 17, wherein said mechanical stop comprises precision spacer balls.

19. The method for assembling a plurality of microdisplay tiles as recited in claim 17, wherein said mechanical stop comprises precision cylinders.

20. The method for assembling a plurality of microdisplay tiles as recited in claim 17, wherein said at least one mechanical stop has been previously fabricated on said optically flat carrier.

21. The method for assembling a plurality of microdisplay tiles as recited in claim 16, the steps further comprising:

polishing said front face and said filling material to a predetermined degree of flatness.

22. The method for assembling a plurality of microdisplay tiles as recited in claim 21, wherein said polishing step comprises chemical/mechanical polishing (CMP).

23. The method for assembling a plurality of microdisplay tiles as recited in claim 21, wherein said predetermined degree of flatness of said front face is within a dimension less than the wavelength of light.

24. The method for assembling a plurality of microdisplay tiles as recited in claim 16, wherein said releasably attaching step (c) comprises using a vacuum technology.

25. The method for assembling a plurality of microdisplay tiles as recited in claim 17, wherein said releasably attaching step (c) comprises using an adhesive technology.

26. The method for assembling a plurality of microdisplay tiles as recited in claim 25, wherein said releasably attaching step (c) comprises curing media with one or more of the set of heat, infrared energy, ultraviolet light, pressure, chemical reaction and time.

27. The method for assembling a plurality of microdisplay tiles as recited in claim 16, further comprising the step of bonding to said common substrate.

28. The method for assembling a plurality of microdisplay tiles as recited in claim 27, the steps further comprising:

repolishing said mirror array to a predetermined optical precision, if required.

29. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 1, wherein said three-dimensionally arranging step (b) comprises arranging said plurality of microdisplay tiles with respect to a direction substantially perpendicular to the plane of said front faces of said microdisplay tiles.

30. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 29, wherein said three-dimensionally arranging step (b) further comprises arranging said plurality of microdisplay tiles with respect to at least one of two orthogonal, lateral directions parallel to said faces of said microdisplay tiles.

31. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 29, wherein said optically flat carrier is a removable optically flat carrier.

32. The method for assembling a plurality of microdisplay tiles as recited in claim 29, wherein said plurality of microdisplay tiles comprises a mirror array.

33. The method for assembling a plurality of microdisplay tiles as recited in claim 32, further comprising the step of:

polishing said mirror array to a predetermined optical precision.

34. The method for assembling a plurality of microdisplay tiles as recited in claim 29, wherein said arranging step (b) results in at least one gap between at least two of said plurality of microdisplay tiles.

35. The method for assembling a plurality of microdisplay tiles as recited in claim 34, wherein said filling material applying step (d) results in substantially filling said at least one gap between at least two of said plurality of microdisplay tiles.

36. The method for assembling a plurality of microdisplay tiles as recited in claim 35, wherein said filling material comprises at least one from the group of epoxies, acrylics, silicones, and other polymeric materials.

37. The method for assembling a plurality of microdisplay tiles as recited in claim 36, wherein said filling material is filled with at least one from the group of diamond, boron nitride, silicon carbide, aluminum nitride, other ceramic materials, and glasses.

38. A method for assembling a plurality of reflective microdisplay tiles into a single, liquid crystal module, thereby forming a tiled, reflective microdisplay capable of generating a projected image having visually imperceptible seams, the steps comprising:

a) providing a plurality of monolithically fabricated microdisplay tiles, each having a front, active face, a rear, mounting face, at least one precision finished edge, and a substantially rigid integrated circuit backplane, each of said microdisplay tiles comprising an array of pixel electrodes having a predetermined, substantially uniform pixel pitch, and having a thickness greater than said pixel pitch;

b) laterally arranging said plurality of microdisplay tiles such that said at least one precision finished edge of a first one of said plurality of microdisplay tiles is adjacent said at least one precision finished edge of a second one of said plurality of microdisplay tiles, the distance between adjacent pixels proximate said precision finished edges being substantially equal to said predetermined, substantially uniform pixel pitch;

c) vertically arranging said plurality of microdisplay tiles parallel to an optically flat common reference plane such that a space between said front, active face of each of said plurality of microdisplay tiles and said common reference plane is substantially equal for each of said plurality of microdisplay tiles, said spaces being smaller than the wavelength of visible light, said vertically arranging step (c) comprising the sub-steps;

i) releasably attaching said front, active faces of said plurality of microdisplay tiles to an optically flat carrier; and

ii) thereafter, when required, polishing said rear faces of said plurality of microdisplay tiles;

d) after said vertically arranging step (c), attaching said rear, mounting faces of each of said plurality of microdisplay tiles to a common support substrate such that said lateral and vertical tile alignment is maintained, thereby forming a tiled microdisplay array;

e) releasing said plurality of microdisplay tiles from said optically flat carrier;

f) after said attaching step (d), polishing said front, active faces of each of said plurality of microdisplay tiles to a precision of less than approximately 100 nM; and

(g) assembling said tiled microdisplay array into a tiled, reflective microdisplay assembly by adding a perimeter seal, liquid crystal and a common cover plate.

39. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said optically flat carrier comprises a temporary carrier and said common substrate comprises a permanent substrate.

40. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said laterally arranging step (b) comprises aligning said plurality of microdisplay tiles to at least one alignment mark on said optically flat carrier.

41. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 40, wherein at least one of said plurality of microdisplay tiles comprises a tile alignment mark adapted for registration with said at least one alignment mark on said optically flat carrier.

42. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said releasably attaching sub-step (i) comprises using a vacuum technology.

43. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said releasably attaching sub-step (i) comprises using an adhesive technology.

44. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 43, wherein said releasably attaching sub-step (i) comprises curing an adhesive using at least one of the techniques:

heat, infrared energy, ultraviolet light, chemical reaction and time.

45. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said polishing step (f) comprises chemical/mechanical polishing (CMP).

46. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said laterally arranging step (b) comprises aligning said plurality of microdisplay tiles relative to at least one mechanical stop.

47. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 46, wherein said at least one mechanical stop comprises one of the group of materials:

polymers, ceramics, glass and metals.

48. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 46, wherein said at least one mechanical stop comprises precision spacer balls.

49. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 46, wherein said at least one mechanical stop comprises precision cylinders.

50. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 49, wherein said at least one mechanical stop has been fabricated on said optically flat carrier prior to said laterally arranging step (b).

51. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said plurality of microdisplay tiles comprises a mirror array.

52. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 51, wherein said polishing step (f) comprises polishing said mirror array.

53. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 51, wherein said assembling step (g) comprises the sub-step of:

i) dispensing said perimeter seal around a periphery of a front face of said tiled microdisplay array.

54. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 53, wherein said perimeter seal includes a liquid crystal fill port.

55. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 53, wherein said common cover plate comprises a common glass plate and wherein said assembling step (g) comprises the additional sub-step of:

ii) attaching said common glass cover plate to said perimeter seal thereby forming a cavity between said front, active faces of said plurality of microdisplay tiles and said common glass cover plate.

56. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 55, wherein said assembling step (g) comprises the additional sub-step of:

iii) filling said cavity with liquid crystal material.

57. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 38, wherein said common cover plate is substantially transparent.

58. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 57, wherein said common cover plate comprises at least one from the group:

mask, optically transparent electrically conductive layer and liquid crystal alignment layer.

59. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 58, wherein said optically transparent electrically conductive layer comprises indium tin oxide (ITO).

60. The method for assembling a plurality of reflective microdisplay tiles, as recited in claim 58, wherein said liquid crystal alignment layer comprises polyimde.